What, I wonder, does the past smell like? Is it that leathery, perfumey smell of the inside of Auntie Vera’s handbag? Or is it the dry, clean smell of my father’s shaving cream?

Smell and memory are powerfully linked. The waft of a scent from across the room, the drift of something agricultural in the car window, the yeasty warmth of a fresh loaf, all these can trigger powerful memories.

Sure didn’t our old friend Marcel Proust got a whole seven-volume novel out of what happened when his narrator first smelled and then tasted a freshly baked madeleine cake.

That mix of mint and sweat from sports changing rooms can transport me back to Bective rugby club circa 1985.

And don’t mention that cologne female Spanish students used to lather on like sheep-dip back in the 1970s.

These days, thanks to chronic allergies and years of inhaling Spanish cologne, my sense of smell is all but gone.

Which is a pity, because scientists have recently discovered what our favourite smell is, and why.

Toast, according to the boffins at Cardiff University, is one of the most universally loved smells. Not burnt toast, mind you, but that golden, just-done toast that is crunchy on the outside and still a little doughy on the inside.

It’s because the smell of toast reminds us of happy childhood memories. Toast is often one of the first solid foods children encounter, and the smell gets imprinted early and deep.

Toasted bread does seem to loom large in the imaginations of a certain kind of English nostalgist.

“All that’s required is a consistent smell, combined with an event powerful enough to pin a given emotion to that particular set of chemicals,” says Professor Tim Jacobs.

Apparently it’s to do with the sugars caramelising in the dry bread and releasing that distinctive smell.

Toasted bread does seem to loom large in the imaginations of a certain kind of English nostalgist.

TV chef Nigel Slater called his memoir simply ‘Toast’, while cookery writer Elizabeth David devoted whole chapter in one of her books to the stuff. She was particular lyrical about the sound of butter being scraped on toast.

Yet toast, despite what you might think, is not that easy to get right, according to an expert friend of mine.

“I just had to send the toast back,” she said of the breakfast offering at a top Irish hotel. “I know there’s a recession on, but some standards have to be maintained.”

For her, the colour must be even, and the butter must be applied (right out to the edges, mind!) within, oh, about 20 seconds of the toaster popping.

I’ve seen her in action in her own kitchen and it’s like a Western variation of the Japanese tea ceremony.

The butter is softened in a dish over the toaster as the bread itself is toasting below. Her toaster, which has more dials that the flight deck of the Boeing Dreamliner, is calibrated to precise measurements.

When it pops, the bread is grabbed and the butter applied in a sequence of movements so fast that you’re not really sure you saw it at all.

My wife is simply not in the same toast league. The only time I saw her become exercised about toast was shortly after the birth of our daughter.

“Just you wait,” she her friend who had given birth some weeks before, “when they bring you that cup of tea and slice of toast, you’ll forget all about the labour and the birth. It’ll be the best slice of toast you’ll ever eat.”

This mythical slice of Holles Street toast became something of a joke between us in the lead up to the due date.

Trouble sleeping? Baby pushing on your bladder? Nipples cracking? Never mind. It’ll all be but a memory when they bring you that slice of magic toast.

The birth, when it came, went without a hitch. I mentioned the toast to my wife several times as an incentive to push or breathe, until she told me where I could stick it.

Then, in that little bubble of calm that follows the birth, my wife and I were sitting with our new baby and watching the dawn come up over the city.